In the field of displays, LED's are often used to convey information regarding the status of a device. This is especially true in the field of computer networks, where the status of different parts of the network are represented by whether or not an LED within a display is enabled or lit-up. Therefore the number of LED's that are enabled or lit at any one time can vary from zero to the maximum number of LED's. The amount of current needed to drive the display, therefore also changes. Providing a current supply which is variable from practically zero when no LED's are enabled, to the maximum current needed to enable all the LED's, can be expensive and difficult to incorporate. This is especially true when the display device is substantially all digital logic.
Also, very often a plurality of LED's are arranged in a matrix arrangement with a plurality of rows and columns. In order to simplify the selection of individual LED's, one terminal of each LED in a row is connected together. The second terminal of the LED's in a column are also connected together. In order to enable a specific LED, the row of first terminals and the column of second terminals for that specific LED are energized. To further simplify operation of the LED matrix, the rows are energized sequentially and only the columns having LED's to be lit, are enabled. If a variable current supply is used to power the rows, it must be very quickly and efficiently switched and varied sequentially through the rows. The structure for performing this operation is an added expense.